<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>百分比布局</title>
    <style>
        * {
            box-sizing: border-box;
        }
        
        body>* {
            width: 95%;
            height: auto;
            margin: 0 auto;
            margin-top: 10px;
            border: 1px solid #000;
            padding: 5px;
        }
        
        header {
            height: 50px;
        }
        
        section {
            height: 300px;
            border: none;
            padding: 0;
        }
        
        footer {
            height: 30px;
        }
        
        section>* {
            height: 100%;
            padding: 5px;
            float: left;
            border: 1px solid #000;
        }
        
        .aleft {
            width: 12%;
        }
        
        article {
            width: 74%;
            margin-left: 1%;
        }
        
        .aright {
            width: 12%;
            margin-left: 1%;
        }
    </style>
</head>


<body>
    <header>头部</header>
    <nav>导航</nav>
    <section>
        <aside class="aleft">侧边栏左</aside>
        <article>文章</article>
        <aside class="aright">侧边栏右</aside>
    </section>
    <footer>页脚</footer>
</body>

</html>